This study investigated the temperament characteristics of a sample of children from 7 to 14 years old, verifying the influence of genetics in the determination of temperament. A sample of 26 parents provided data about temperament of 26 pairs of twins (15 monozigotic, 11 dizigotic), totalizing 52 subjects. For the data gathering, the Pavlovian Temperament Survey - PTS, child version was used, which investigates three temperament factors: Strength of Excitation (SE), Strength of Inhibition (SI) and Mobility (MO). The results showed that, from parents' perception, this sample had mobility as the predominant temperament characteristic. Analysis of variance (MANOVA) indicated that temperament characteristics varied when considering variables such as sex and age group. The correlation obtained from pairs of monozigotic and dizigotic twins made evident the influence of genetic determination on the three factors.